Abstract. Dynamic monitoring of geological hazards is an important project. Photogrammetry plays an important role in geological hazard monitoring, because of its advantages of convenient data processing, low cost, non-contact, direct texture information and intricate 3-D real scene model. For the traditional photogrammetry can not meet the needs of dynamic monitoring, based on multi-period nap-of-the-object photogrammetry, this paper obtains high-precision images and produces a refined 3D real scene model to carry out the dynamic monitoring of geological disasters. A deformation detection method of geological hazards based on the comparison of three-dimensional model differences is proposed to locate the position with serious deformation. Then, based on the severely deformed area, the multi-period generalized orthophotos are produced, and the image feature matching is used to find the homonymous points between the generalized orthophotos. The two-dimensional and three-dimensional coordinate forward and inverse transformation of the generalized orthophotos are used to calculate the size and direction of the deformation displacement, analyze the deformation trend of geological disasters, and finally realize accurate monitoring of the deformation trend of geological disasters. The results show that the deformation area detection method proposed in this paper is simple and effective, which can quickly find the deformation position. The deformation trend prediction based on multi-period generalized orthophotos is feasible, and the displacement with deformation of 3CM can be accurately pointed out.